1. Field of the Invention
The present invention relates to a radiation cassette including a casing for storing a radiation image recording medium, and a light shielding plate for holding the radiation image recording medium in a light-shielded condition, the light shielding plate having a lid openably and closably mounted on at least a portion of the casing, and a method of manufacturing such a radiation cassette.
2. Description of the Related Art
There is known a system for recording radiation image information of a subject such as a human body with a stimulable phosphor, and reproducing the recorded radiation image information on a photosensitive medium such as a photographic film, or displaying the recorded radiation image information on a display device such as a CRT or the like.
The stimulable phosphor is a phosphor which, when exposed to an applied radiation (X-rays, xcex1-rays, xcex3-rays, electron beams, ultraviolet radiation, or the like), stores a part of the energy of the radiation, and, when subsequently exposed to applied stimulating rays such as visible light, emits light in proportion to the stored energy of the radiation. Usually, a sheet provided with a layer of the stimulable phosphor is used as a stimulable phosphor sheet.
It has been practiced to apply a radiation, e.g., X-rays, to a subject such as a human body or the like to record the radiation image information of the subject directly on a photographic film. When the photographic film is developed, the recorded radiation image information is turned into a visible image, which will be used for medical diagnosis or the like.
Radiation image recording mediums such as stimulable phosphor sheets, photographic films, or the like are usually stored in respective cassettes. When a cassette with a radiation image recording medium stored therein is loaded into an exposure apparatus, X-rays representing radiation image information are applied to the radiation image recording medium through the cassette.
If a face plate of the cassette which is to be irradiated with X-rays were integrally molded, then the face plate would tend to entrap foreign matter, have reduced mechanical strength, and suffer a reduction in the X-ray transmittance. One known cassette that has been proposed to eliminate the above shortcomings comprises a flat plate made of a carbon sheet, an aluminum sheet, or the like and four side frame members made of a plastics or the like according to an insert molding process.
However, when the frame members are molded of a resin such as plastics, they are liable to suffer molding shrinkage. Therefore, the four sides of the cassette are unduly warped or deformed. Large-side cassettes thus manufactured are likely to have a considerably large amount of warpage or deformation thus introduced and hence to become defective. One solution would be to mold cassettes of a resin which is less liable to cause warpage, e.g., a resin containing glass fibers or the like. However, such a resin is of poor appearance.
When a cassette storing a stimulable phosphor sheet is loaded into a radiation image reading apparatus, the stimulable phosphor sheet is removed from the cassette and repeatedly fed in the radiation image reading apparatus. Therefore, the stimulable phosphor sheet tends to be electrically charged. If the cassette has a face plate made of a carbon sheet, then since the carbon sheet is an electrically conductive material, the electric charge is transferred from the stimulable phosphor sheet via the cassette to human hands or other objects when the cassette storing the stimulable phosphor sheet is removed from the radiation image reading apparatus.
It is a general object of the present invention to provide a radiation cassette which is of a simple structure, can be manufactured according to a simple process, is free of deformations, and has high quality, and a method of manufacturing such a radiation cassette.
A major object of the present invention to provide a radiation cassette which is of a simple structure to reliably prevent an electric discharge from occurring from a radiation image recording medium via the radiation cassette to an external object.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.